Etching machine



Feb. 16, 1954 J EASLEY ET AL 2,669,048

ETCHING MACHINE Filed NOV. 26, 1952 4 Sheets-Sheet 1 INVENTORS. John A. Eas/ey n/ly/iam E. Eaen By Harry E. 6way3e MXM A TTORNEYS Feb. 16, 1954 J. A. EASLEY ET AL 2,669,048

ETCHING MACHINE Filed Nov. 26, 1952 4 Sheets-Sheet 2 INVENTORS. John A. Eas/ey Wf/fiam 5. Eden Harry E. Ski 01,66.

A TTORNEYJ' I F 6. 1954 J. A. EASLEY ET AL 2, 6 ,048

ETCHING MACHINE Filed Nov. 26, 1952 4'Sheets-Sheet 3 INVENTORS. {ft}: 5 John/I. [as/e3 W/Y/l'd/Y 15 Eden- Harry E. Ski 033a B) a Z 4 ATTORNEYS FeB. T671954 J. A. EASLEY ET AL 7 2,669,048

ETCHING MACHINE Filed Nov. 26, 1952 4 Sheets-Sheet 4 k INVENTO RS Jo/m A. E as/ey WM/mm 5 Eden By Haw/g5. Sn/0x36 A TTORNE Y5 Patented Feb. 16, 1954 ETCHINGi MACHINE Jiohm Aa-Easlex', William E. lld'engsand Harn'y swayze Mid-landinMich assignoizsf tm'iheizDow Chemical. Comma: Midlands}. Mich;, a corp.0-

ration of Delaware;

A'ppli'cation Novemberzfi, 952, Se 3223650 tcla-imss. (Cl. Mir- The; inventions relatesir to: etching machines;

especialiy: those: adapted-tor etch metal plates,

such asprintinga plates andtthe :like. The invention? more particularlyconcerns: an:.. improved2 etching machine of. the type: wherein the worktoxbeaietchediis heldi-over-a tankiofi etching: acids. andzthes acid is .splasheda against thework megns=.-rofr rotating paddles whichidipinto the act In conventional etching-i machines; of the type' with which; the invention isconcerned; therexis; the -difliculty thatthe plates are not alwaysuni fotmlyzetched. This; difliculty', We have found; is due; to the-afact: .thatzsome; portions of the plate: undergoing etching; persistently receive a more vigorous: splashing of etching acid than others. It'is one t thelprincipal objects of thefinvention to onereomeythis difiicultyby providing means for ensuringia' uniformtactioni of the acid on all por-i tionsz-ot theiworkso-that during thestime theworkr: is .beingzetohed each portion will on the average receiuerthe same'xarnount: oft splashing and the impinged: acid will produce a uniformv etch over alleltheexposeds portions of the. work. This object-1. is attained accordingto the invention by. provide. ingfmeansv for? givingithei' worka random motion whilezthe etching: acid is splashed against! the work: Othenobj'ects. and. advantages of the: ill-- venti'onnwill' appear from the; following descriptiom-and' accompanying drawimg; illustrating a: preirredi. embodiment of. the: invention.

Fig. 1 is a plan] View of ithe apparatus .withi the cover lowered into place over the etching acidi tai'mkj!v someii-parts. off the. cover being cut away to show internal structure;

2 isa: vertical cross: section on; the line "2. 2

of-Fi g. 1.:

Fig. 3iis -a= rear-elevation of: a-v portion of the apparatus with th'e cover lowered. intoplace'ovet- V 2 drainingthe tankt- Dependingifrom: the inside eitherimfl ofthetanhaleng one side and offset therefir'om :is an H upstanding bafiie. I 0, the lowen edge of which is above the bottom 5 of thetank- 1 Insideth'extank just below the rim 9 1 along the frontg rearpone sideandihaffie wisalledge H in the'formi of pieces of angle iron-secured 'to the:

said baflie andifsidesl of the tank. The ledge-i stiifens-the rim-of the tank-and: baifie l0: and formsaisupport forthe'cover lz2iwhich rests upom theded'ge tl whenv the cover istinithel positioninw which. it forms a closuretfor'theitanlc as-in-E'ig; 1.

As? shown; the cover IZ is a rectangulari'metalz platetwhzich isijust largelenough ito lie insicle'the-- is facilitatedsfbythe armsetl' while the rear edge l Si'is carried: byxthe wheels. Isa-which are attached-:1 to the rear of'the. cover andnride" on the ledge H as. the front edge otthecover is raised, as by the: handle as. As shown; the arms: are jouifinalled onracro'ss bar Z I" which is supported at'eachend lay thecolumns'2'2 attached to the legs? 4. One end of each: pofi' the arms is. fixed too a. counterweight 23 and the other: en'dofeach of the arms is pivoted in a bracket-24': which 'is secured to the upper side of thecover;

one side of the tank just belbwtheledge- H is provided-with an" opening 25 communicating" with a fiiie 25 fe1 ventingfumesfrom the tank; Insideth'e-tank opposite the opening is a -bafiie 2 to prevent the escape of acid spray during opera tiona Along the inside of and offset from the front za ana': rear-'- ZBofthetank are bafii' es and- 3 l-, respective-1y;

Arranged across thetankin a plane and spaced" above' the bottom is a series of paddle shafts 32* which pass through openings 33' and 3 4 in the front and 'rearsi'd'es of the" tank-g respectively; and openings '35 and: 3t in theadjacent' bafiles, 36 and'-3-l-; respectively. The shaftsarejournall'ectinbearings ttwhichare' mounted on brackets"a attachedto the legs 4; Near-eachend -of each shaft between; the tank and the adjacent haiile i'sya spinner ring- 39 which in com-,

binati'bm with adjacent bame prevents escape of acid spray through openings 33 and 34 in the tank during operation. Each shaft carries a paddle blade 40 formed in two parts 4| and 42 clamped on to and extending the length of the shaft between the baffles 30 and 3|, the width of the paddle blade being sufficient to permit the outer edges to dip into the etching acid when the tank is appropriately filled with acid for etching. With this arrangement of paddles, the working depth of the acid in the tank will be below the openings 33 and 3% in the sides of the tank through which the paddle shafts pass but above the outer edges of the paddle blades when the latter are turned into the vertical plane. Between each of the adjacent paddle blades is a vertical baille 43 which is mounted at either end on the front and rear bafiies 30 and 3|.

On one end of each paddle shaft is mounted a pulley 44, and, by means of three belts 45, 46, and 41 each engaging two of the paddle shaft pulleys, all of which are the same diameter, and a sheave of the multisheaved motor pulley 4B, the paddles are driven at the same speed by motor l9.

Means for controlling the temperature of the etching acid are provided as by a heat exchanger in the form of the pipe coil 50 which is disposed on the inside of the bottom of the tank below the paddle blades. The pipe coil has an inlet which is connected to a source of heat transfer fluid (not shown) at a desired temperature and an outlet 52 for the heat transfer fluid which traverses the pipe. The inlet and outlet are arranged to enter the tank between the side or" the tank and the upstanding baiile Hi thereto adjacent. As a means to ensure homogeneity of the etching bath composition during operation (in addition to the agitation produced by the paddles) pipes 53 and 54, provided with small openings 55 along the sides, are arranged in the tank adjacent to the pipe coil. The pipes are connected together and to the delivery side of a circulation pump 56 by a pipe 57 while the suction side of the pump is connected to the drain I by a pipe 58. Pipes 53 and 54 enter the tank between the side of the tank and the upstanding balile l0 thereto adjacent. The circulation pump 56 may be driven by motor 49 through the belt 59.

The work to be etched, e. g. a printing plate 60, is held on the underside of the cover on the work holder plate it by means of clamps 6! and 62. As shown, one of the clamps, for example 6|, is secured to the work holder plate by means of bolts 63, the other is clamped in a slot 64 in the work holder plate by clamping screw 65 so that the distance between the two clamps is adjustable to permit clamping in place work pieces of various sizes. The work holder plate i6 is mounted for rotation in a plane parallel to the cover on the lower end of the shaft 65 which extends through a slotted opening 61 in the cover.

The other end of the shaft is journalled in bearings 68 which are mounted upon a carriage plate 69. The carriage plate is mounted on bearings which are adapted to slide on ways 1| mounted on the top of the cover.

As shown, the shaft 66 carries a pinion 12, the teeth of which are adapted to engage the teeth 13 at either end of a rack 14, secured to the cover, as the carriage plate is reciprocated back and forth along the ways H from one end to the other. The toothed portion of one end of the rack is longer than the toothed portion at the opposite end and asymmetrically placed with respect to the midpoint of the rack as shown particularly in Fig. 6. The reciprocatory movement is imparted to the carriage plate by the connecting rod I5 one end of which is pivoted to the bracket 16 on the carriage plate and the other pivoted to the crank 11 of the speed reducing gear box 18. The speed reducing gear box is driven by motor 19 through belt 80. With this arrangement, a rotational motion is given to the work holder plate It while the carriage plate is moved along the ways and the pinion engages the rack but not when the pinion is between the toothed portions of the rack, in the space 8|, in which the pinion does not engage rack teeth but is free to coast.

In operation, sufficient etching acid is placed in the tank I to bring the upper surface 82 of the etching acid bath to about A; inch, for example, above the periphery of the path of revolution 83 of the paddle blades as shown in Fig. 2. Before starting the apparatus, the cover I2 is lifted upwardly at the front edge by means of handle 2|) into the position shown in Fig. 4 so as to give access to the underside of the cover and the work holder plate It. The work to be etched, e. g. a printing plate E50, is fixed against the work holder plate It between clamps 6| and 92 which grip the opposite edges 8 and 85, respectively, of the printing plate. The cover I2 is then lowered into position on the ledge II as by pulling handle 26 forward and downward.

By setting into operation motor 49, paddles 40 are revolved thereby splashing etching acid upwardly against the work on the work holder. At the same time, motor :39 drives pump 55 which withdraws etching acid from the tank and squirts it through openings 55 in pipes 53 and M in the etching tank. Motor i9 is also started along with motor 49, thereby oscillating the carriage plate and giving the work holder plate a random oscillatory and translatory motion in a horizontal plane. The nature of this motion will be apparent on inspecting the drawing particularly Figs. 2 and 6. From these figures, it is evident that as the crank TI is revolved the carrier plate 69 oscillates back and forth on the ways "i I. As the carrier plate moves from left to right as seen in Fig. 6, for example, pinion l2 turns clockwise at a rate determined by the speed at which the carrier plate moves the pinion along the toothed portion at the left end of the rack 14, until the pinion 12 reaches the space 8| where there are no teeth on the rack. When the pinion 12 reaches the space 8|, the pinion is no longer driven by the rack and instead the pinions rate of rotation decreases since it merely coasts while it is carried along the space 8|. ment to the right causes the gear to engage the toothed portion on the right hand end of the rack and the speed of rotation of the gear is thereby increased and again determined by the rate at which the carrier plate 69 is moved by the crank Tl. When the carrier plate reaches the extreme right of its travel, the plate stops and then reverses its motion. As a consequence, pinion 12 also ceases to rotate momentarily while its translational motion changes direction, moving thereafter from right to left until the carrier plate moves to the extreme left of its travel. In moving from right to left, the motions of the pinion 12 are similar but opposite to its motions as described in proceeding from left to right.

Since the carrier plate E6 is mounted on the shaft on which pinion i2 is rigidly affixed, the carrier plate undergoes the same rotational and trans- Further. move lational motions which are random with respect to the points of impingement of the acid etching bath splashed upon the printing plate by the paddles. The randomness is achieved by virtue of the coasting feature which is built into the rack, i. e. the space 8|. This space allows the rotational speed of the plate to decline quite rapidly while the pinion 12 moves from one toothed portion of the rack to the other. With this arrangement of rack teeth 13, space 8|, and pinion I2, any selected portion of the surface of the work exposed to the acid bath never passes over the same spot above the bath very often during the time the work is subjected to the splash of the etching acid.

A desirable rate of rotation of the work holder plate is from about 1 to 40 R. P. M., a preferable rate being from 2 to R. P. M. The translational motion, i. e. the back and forth motion of the plate may range from about 1 to 10 cycles per minute, a preferred rate being about 2 to 4 cycles per minute. Suitable rotational speeds for the paddles are from about 400 to 1200 R. P. M. It is desirable to make the length of the path of the back and forth motion of the plate holder about as long as the distance between adjacent paddle shaft centers to obtain best results.

We claim:

1. In an etching machine for etching printing plates, the combination of 'a tank adapted to contain a liquid etching composition; a serie of paddle blades having horizontal parallel axes lying in a plane above the upper surface of the etching liquid in the tank when filled to its working level and adapted on being revolved to splash the etching liquid about the tank; upstanding bafiies between the said paddle blades adapted to guide the splashed etching liquid in a generally vertical direction; a removable cover adapted to form a closure for the top of the tank so as to prevent escape of etching liquid on being splashed in the tank; a work holder plate above the baflles below the underside of the cover; motor means on the top of the cover adapted to impart to the work holder simultaneously a translatory and rotational motion in a horizontal plane.

2. An etching machine according to claim 1 having a heat exchanger in the tank below the said paddle blades.

3. An etching machine according to claim 2 6 having perforated pipes adjacent to the heat exchanger, and a pump for circulating the liquid etching composition from the tank through the perforated pipes into the tank.

4. In an etching machine for etching printing plates, the combination of an open top tank adapted to contain a quantity of a liquid etching composition, a series of paddle blades having horizontal parallel axes lying in a plane above the upper surface of the liquid etching composition when the tank is filled to its working depth with the liquid; a vertical bafile between each adjacent paddle blade extending the length of the blade; a ledge on the inside of the tank near the rim, a cover for the tank adapted to rest upon the said ledge, said cover having a slot extending through the center an equal distance on each side of the center; a carriage plate on the top of the cover over the slot; a vertical spindle journalled on the carriage plate and extending through the said slot; a rack on the cover parallel and adjacent to one side of the said slot, said rack having teeth along a portion of each end but not in the portion intermediate the ends; a pinion mounted on the said spindle and adapted to engage the teeth of the said rack on being moved to either end of the rack; reciprocating means secured to the carriage plate for moving the same back and forth in a direction parallel to the said slot, whereby the said spindle is revolved as the pinion moves along either end of the rack; and a work holder carried by the spindle on the underside of the cover.

5. An etching machine according to claim 4 having a heat exchanger in the tank below the said paddle blades.

6. An etching machine according to claim 5 having perforated pipes in the tank adjacent to the heat exchanger, and a pump for circulating the liquid etching composition from the tank through the perforated pipes into the tank.

JOHN A. EASLEY. WILLIAM E. EDEN. HARRY E. SWAYZE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,908,487 Powers May 9, 1933 2,293,201 Gaebel Aug. 18, 1942 2,592,693 Hayms Apr. 15, 1952 

